According to Politico, at least two people, former Russian spy Sergei Skripal and his daughter Yulia, “have been left extremely sick due to the alleged nerve agent.”

A former agent with Russia’s FSB secret service, Colonel Skripal arrived in Britain in 2010 as part of a prisoner exchange, according to The Telegraph. Prior to that he was jailed in Moscow for spying for Britain, the British newspaper said.

Tillerson has described the suspected attack as a “really egregious act,” according to Politico.

“There is never a justification for this type of attack — the attempted murder of a private citizen on the soil of a sovereign nation — and we are outraged that Russia appears to have again engaged in such behavior,” Tillerson said in a statement quoted by Politico. “From Ukraine to Syria — and now the U.K. — Russia continues to be an irresponsible force of instability in the world, acting with open disregard for the sovereignty of other states and the life of their citizens.”

British Prime Minister Theresa May said on Monday it was “highly likely” that Russia was responsible for the Salisbury attack, Politico reported.